With the advent of self-cleaning ovens there has been an even greater need for treatment of the carbonaceous components of the fumes passing from the oven. Various oxidation units have been developed and used quite successfully as a component of self-cleaning ovens to effect conversion of the hydrocarbon products. Exemplary of the various types of structures and prior art efforts are those disclosed and claimed in the following U.S. Letters Patent: Scofield U.S. Pat. No. 2,862,095 granted Nov. 25, 1958; Hurko U.S. Pat. No. 3,121,158 granted Feb. 11, 1964; Hurko Pat. No. 3,290,483 granted Dec. 6, 1966; Dills et al. U.S. Pat. No. 3,364,912 granted Jan. 23, 1968; Faehling et al. U.S. Pat. No. 3,549,859 granted Dec. 22, 1970; Brucken U.S. Pat. No. 3,782,360 granted Jan. 1, 1974; and Burstein U.S. Pat. No. 3,785,778 granted Jan. 15, 1974.
Various types of catalytic materials have been proposed for use in such converters, some being spiral wound wires or filaments, some being catalyst beads, some being catalyst-coated refractory materials, and some being a coated screen. A common problem encountered in such converters is that of differential expansion of the catalyst component relative to its surrounding housing, and that has been particularly acute when refractory materials have been employed. When the metal housing expands substantially, the ceramic block tends to be free to move excessively within the housing and is particularly susceptible to injury due to impacts or shocks while in this relatively unrestrained condition.
It is an object of the present invention to provide a catalytic oxidation unit for ovens and the like utilizing a block of cellular ceramic material with a catalyst coating which is firmly supported within a metallic housing over the entire range of operating temperatures.
It is also an object to provide such a catalytic oxidation unit which may be fabricated readily and relatively economically and which is simple to install in an oven or like unit.
Another object is to provide such a catalytic oxidation unit employing a relatively fragile honeycomb ceramic block having a surface coating of oxidation catalyst on the walls of the cells thereof.